Plain Cylindrical Ring Gages also referred to as Plain Cylindrical Ring Gauges are used to check the outside diameter limit on manufactured parts. Cylindrical ring gages are also used as masters for setting air gages, bore gages and internal micrometers. When they are used to check a part directly, the cylindrical ring gages are referred to as GO and NOGO. The GO checks the upper limit of the part tolerance while the NOGO checks the lower limit. Plain cylindrical ring gages are available in steel, chrome, and carbide in Class XXX, Class XX, Class X, Class Y, and Class Z in inch or metric.